Field of the Invention
The present invention relates to a method and the like for resin-encapsulation of electronic components on a board.
Description of the Background Art
A conventional method of resin encapsulation, used in manufacturing a semiconductor package as an example of a resin mold product having electronic components mounted on a board will be outlined in the following.
In the conventional method of resin encapsulation, first, a printed circuit (wiring) board (hereinafter simply referred to as a board) having semiconductor chips (hereinafter simply referred to as chips) as exemplary electronic components mounted thereon is prepared. Thereafter, on one of a pair of molds having one mold and the other mold positioned opposed to each other, the board is placed. Then, the mold pair is closed. Thereafter, through a resin flow path, melted resin is introduced into a cavity provided in the other mold of the mold pair. At this time the melted resin is pressurized.
Thereafter, the introduced resin sets. Thus, a resin molded product is formed. Then, the mold pair is opened. The resin molded product is taken out from the one mold. Then, the resin molded product is diced and divided into a plurality of semiconductor packages. Thus, a semiconductor package as a final product is complete.
Recently, the number of terminals of the semiconductor chip has been increased as compared with conventional chips. Further, a structure has been used in which semiconductor chips are stacked on a board. Further, the semiconductor package has been made thinner.
In addition, wires electrically connecting the semiconductor chip to the board have been made longer, and the space between adjacent wires becomes narrower. As a result, the conventional method of resin molding described above tends to cause the following problems.
First, it has become more likely that the wire is deformed or disconnected because of the flow of the melted resin introduced into the cavity. Further, it has become more likely that adjacent wires are undesirably brought into contact with each other. In order to solve such problems, it may be helpful to decrease the speed of introduction of the melted resin into the cavity. When the speed of introduction of the melted resin is decreased, however, the melted resin that is being introduced comes to have higher viscosity. This makes it difficult for the gas in the melted resin to escape to the outside. Accordingly, voids or unfilled portions tend to result in the set resin mold.
Further, recently, there is a demand for the boards of larger size, in order to reduce cost for semiconductor products. When electronic components are to be resin-encapsulated on a large board, flow distance of the melted resin becomes longer than when the electronic components are resin-encapsulated on a small board. This increases the possibility of voids or unfilled portions mentioned above.
It is also noted that the resin may undesirably set on the resin flow path. The resin set on the resin flow path is discarded, and therefore, the conventional method of resin encapsulation involves the problem of waste of resin material.